Are you sure it has R/A Heads cause realisticaly all D port Pontiac Head's are the same, `68-70
If it is a 366 Horse R/A V8 then all that's different from a standard 350 HP 400 is the cam and the tune.
A Comp Cams Magnum 270H is a great performer and can be used with a stock stall.

 

I've always been partial to Dart heads, but there are a lot of good heads out there. I'm no head porter or cam designer, and I would be asking these guys the same kind of questions. The Dart Pro 1 CNC heads would be a great out of the box head for you I think. It's a 227cc runner which is probably a little smaller than optimal for a 427 but I think it would make for good street manners. Again I can't stress enough how little I really know compared to some of the other guys on this board. Give me a while and I can probably find a good cam to go with those heads, but if you called Comp Cams after you decide on everything else they can get you what you need.

Shortblock refers to the block with the rotating assembly (crank, rods, pistons). To some people that even covers the cam. Longblock refers to shortblock + heads (sometime without the valvetrain). You can buy a rotating assembly with 4" crank and 4.155" bore and rods the right length already balanced and ready to be installed.

A 427 is capable of well over 800 hp naturally aspirated with the right set of heads and everything else spot on. I think 500hp should be pretty easy.

Let me look around and see if I can find you a good deal on a rotating assembly and then a cam that would work well with those heads. You may very well be better off calling comp cams and asking them though, last time I talked to them they had some good knowledgeable help.

 

WOW this thread is confusing, I think some of you guys are talking about Chevy 400's and the others are talking about the Pontiac's....

 

Yeah I was talking about Chevy 400s with giwanabe, seeing as how the motor is from his Impala I assumed it was an SBC.